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Xj550 with a xj650 head and bigger bores?

Discussion in 'XJ Modifications' started by Kweb1889, Oct 11, 2020.

  1. Kweb1889

    Kweb1889 Member

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    I have an opportunity to pick up a 1980 xj550 maxim and I was wondering if I could take the xj650 that I have and swap the bigger head with bigger bores kinda like mezzmo did the 650 with 750 heads??
     
  2. a100man

    a100man Well-Known Member

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    Nope.
    But FJ/XJ/FZ/YX600 - yes.
    Is worth it ? Debatable.
     
  3. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Correct. Cranks and bottom ends way too different. If you want to make a "monster" 550 you'd need to stay within the same family of motors, as above.

    Easier to just pop a whole 600 into the 550 frame; that's what Yamaha did when they created the Radian.
     
  4. Minimutly

    Minimutly Well-Known Member

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    And then gave it half a fuel tank....
     
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  5. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Style man. Style.
     
  6. Kweb1889

    Kweb1889 Member

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    So the 650 will work with the 750. But the 550 wont work with the 650. I'm assuming this is because one is shaft driven and the other is chain driven? I picked up the xj550 anyway I do have one question other than the swap is 24000 miles a lot for this bike is their any maintenance that should be done? Besides clearance I am gonna do that I know it's a regular thing that you should do.
     
  7. Kweb1889

    Kweb1889 Member

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    Ok but that's only a 50cc jump would that even be worth the effort? lol. Are their any mods that I could do to beef up this 550 motor?
     
  8. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    The XJ550 Seca had hotter cam(s). I don't recall the details, if it was both cams, or just one and what the HP gains were. The seca was rated at 50 HP.
     
  9. XJ550H

    XJ550H Well-Known Member Premium Member

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    no 80 550 it is an 81.
    what do you want out of the bike faster or quicker?

    you can push past redline and get to 120mph but not recomended for long duration.
    you could put a seca rim on the rear and pick up a few mph . in the end the seca tire is not much taller than a maxim tire. if you want to keep the swirl wheel pick up a rim from europe.
    I was talking to someone the other day and he had the death wobble occur at 120mph.
    make sure you have new wheel bearings taper bearings in the head stock and new swing arm bushes to be safe.

    you can go seca cams and would need to upgrade carbs to seca jets and slide needles to get the most out of it.

    you could change sprockets to change top end or quickness but not both.

    in the end you have about a second and a half difference in the 550 and 750 quarter mile with about 17 mph difference in the top end.

    the 750 can be converted to an 820 just like the 650.

    consider the money being spent and you just may want to buy a newer bike to get what you are looking for.

    there is a company selling cams for the 600 which can be put into the 550

    be happy with the bikes you have or buy a newer bike. speed and quickness comes with $$ spent

    there is a thread about a "slightly modified 750" where owner brought the bikes weight down to less than a 550 got quicker but still not faster. weight to HP ratio is what he was going for
     
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  10. Kweb1889

    Kweb1889 Member

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    I am happy with it pretty much got it for free I just have a xj650j that's a project I was just wondering if it would work. The pep was just to get it about 115mph but it sounds like it will already do that thank you everyone.
     

    Attached Files:

  11. Kweb1889

    Kweb1889 Member

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    Alright guys I need some help on my xj550 the shift shaft seal needs replaced the po already removed the pedal but didnt mark it. Question 1 will the seal from my xj650 work? I can order one if I have to. Question 2 can I just put it back on after the seal is done and be good or is their something I have to do to line it up?
     
  12. Minimutly

    Minimutly Well-Known Member

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    1. Buy a new seal
    2. Put it on where it looks right, you'll know as soon as you ride it.
     
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  13. XJ550H

    XJ550H Well-Known Member Premium Member

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    shift lever goes on where it is most comfortable for your foot
     
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  14. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    What seal are we talking about here? This is a 550, there isn't one in the outer cover.

    Oh and if you want to make your 550 capable of 115mph, get it running 100% correctly in stock form and it will come close. The difference between the 550 Seca and Maxim motors was (other than deep carb specs) the Seca's cams have higher lift. Cam timing is essentially the same, valves same diameter, etc. The Seca's airbox also has an odd feature the Maxim's didn't. But the 550 is plenty fast once properly tuned (and you can run it past 9000 rpm in all 5 lower gears.)
     
  15. Kweb1889

    Kweb1889 Member

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    Thank you for the info. And it's the shifter shaft seal I already replaced it with a new one. Now my problem is my peddle has like a ridge inside the threads so it will only go about halfway on not sure what to do. this and my xj650j are my first bikes so I am learning from scratch. And unfortunate I just got this 550 and it has pods and did not come with an air box not quite sure how to tune that either. Maybe re jet if so with what kit?
     
  16. a100man

    a100man Well-Known Member

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    theres no exact answer to this but searching previous posts in this forum will help guide you.
     
  17. Minimutly

    Minimutly Well-Known Member

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    Most folkes on here will tell you to find an airbox, and given this is your first "learning" bike I would agree with them. Get an airbox.
    Re the burrs on the gearlever splines, take a small file to the outside of the ridge, then wiggle the lever until it goes over the remains of them - no magic to this.
     
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  18. lostboy

    lostboy Well-Known Member

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    The bolt must be removed from the shift lever to get it to slip on.
     
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  19. Kweb1889

    Kweb1889 Member

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    The bolt is off it was apart when I got the bike needed a shift shaft seal so I put one on now the pedal is only going halfway on cuz of a ridge in the threads not sure how that happens. A file is what I will try thanks everyone. And of course take the bolt out lol that's common sense
     
  20. lostboy

    lostboy Well-Known Member

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    Sometimes the simplest thing can stump us.
     

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